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How Can I Lower the Humidity in My Shed?

Ventilation is one of the easiest ways to lower humidity in your shed. It works constantly without your having to do a thing once it’s installed. While it seems that it won’t work well during summer days that are humid with no breeze, the convection action inside your shed actually keeps the air moving.

There are several ways to lower humidity in a shed: Use of venting and windows that open, leave a couple of inches of space around the ways for air flow, kitty litter and you can use a dehumidifier.

Warm air, which holds more moisture than cool air, rises and eventually travels out through your roof venting, The movement draws fresh air in through the eave or roofline venting. Even though this incoming air may be humid as well, the movement of the air is what is important and keeps moisture from gathering and condensing inside your shed on either cooler items or on the walls and roof underside. If installing ventilation just isn’t enough, especially if you experience humid summers, you may want to look at a dehumidifier.

What Size Dehumidifier Do I Need for a Shed?

The size of the dehumidifier you need is determined by both the square footage of your shed, the average temperature, and the moisture level inside. These can vary with the seasons and time of day. Fortunately, there are hygrometers to indicate the humidity that are pretty inexpensive. Some models also indicate temperature, and many models are digital.

Some feature stands or holes for hanging on the wall, and some are battery-operated, so they can be left in the shed for readings anytime. Some will even tell you when the humidity is getting too high for the temperature, so you have a clear indication of when to switch on the dehumidifier.

Humidifiers are sized by water-gathering capacity, usually measured in pints. Most home units run from 30 to 70-pint capacity. The relative humidity should be between 30-50%. You’ll often hear the term “relative humidity.” This is a percentage of the humidity needed to achieve the saturation point at the current temperature.

Once you determine the square footage of your shed, take temperature and humidity readings at different times of the day. If it’s the most humid season of the year in your area, you will be better able to judge your dehumidifier size needs.

If not, just allow for a little larger capacity to handle the higher humidity you expect later on in the year. The Association of Home Appliance Manufacturers, or AHAM, has an online chart that will help you choose the right capacity.

What is the Best Dehumidifier for a Shed?

There are actually two main types of electric dehumidifiers that feature two distinct methods of drying the air. The traditional type runs on refrigerated coils much like your home air conditioner. Warm, moisture-laden air is drawn in and flows over the cooled coils where the cold temperature causes the moisture to condense into droplets. It then falls into a collection tub.

The drawback of this type of dehumidifier in a shed is that it doesn’t work well during colder temperatures. The coils can actually become iced up when the temperature gets too cold and the unit stops working. It then has to be defrosted to get it back in operation. Unless your shed is heated, you’ll have problems with this type of dehumidifier.

An innovation was discovered called the hot gas defrost. When the temperature falls below a certain point, the appliance reverses its action, heating up the cold pipes and melting any frozen water. Unfortunately, while it solves the problem of freezing up, it also reduces the efficiency of the appliance.

There is another type called the desiccant dehumidifier. It’s been popular in industrial uses for quite some time for removing huge quantities of humidity from damp storage buildings and the like. This technology has lately been downsized so that people can use this type in homes, garages and sheds. They work by drawing air over rotating discs containing material that absorbs moisture naturally.

The moisture is collected and then the discs are heated at one end as the disc is rotated. This dries them and lets them absorb more moisture. This type of dehumidifier can work at temperatures almost down to freezing, so it’s what you would probably want in your shed. For more information on getting rid of condensation read my article How to Deal with Condensation in Your Shed.

Is a Solar Powered Dehumidifier an Option for a Shed?

Many people who don’t have electricity run to their sheds or who don’t want a higher utility bill love the idea of a solar-powered appliance. However, these units need to run at least 12 hours to really do the job, and most people don’t get that much sunlight per day, even in summer. You’d usually need a battery bank to store energy on days you don’t use the appliance, which some model feature.

All in all, unless you have a small shed, a solar-powered dehumidifier may be just too expensive an option. If you need something that doesn’t run on electricity, a rechargeable battery-operated appliance will cost you much less in the long run. There are many models in many sizes and won’t require the installation of solar panels or connection to those that may be installed on your home.

How to Choose the Best Solar Powered Dehumidifier

Choosing the best solar-powered model rests mostly on determining needed capacity first. Since these appliances operate by passing humid air over refrigerated coils, causing the moisture in the air to condense and drop off into a collection spot, how the individual models handle defrosting is another factor.

The appliance should have a rechargeable battery for times when the solar panel cannot gather enough light to run. It should also have a switch that shuts the unit off when the water tub is full to prevent overflowing if it doesn’t have a connection for a hose to shunt the water

outside. Some models boast quiet operation, but unless you spend hours at a time in your shed, this probably won’t be a consideration.

Should I Install a Humidistat in My Shed?

A humidistat, sometimes called a hygrostat, works much like your home thermostat. Instead of monitoring temperature, it monitors humidity and turns your dehumidifier on and off to automatically control the humidity level. Many dehumidifiers come with this feature built in. It keeps the appliance from running unnecessarily and over-drying the air.

The drawback is that the humidistat usually can only measure the humidity in nearby space. If your dehumidifier is placed out of the way at one end of the shed, the device can sense that the moisture level at that end of the shed is fine and shut the appliance off, while the other end of the shed is still damp.

Placement of the dehumidifier and its humidistat is important, but the sensing capability of the device will still be somewhat limited. Depending on the general humidity of your area or the time of year, one may be desirable, or it may not be necessary. You may also have a musty odor in your shed, check out my article How to Get Rid of Musty Odor in Shed?


If you have a moisture problem in your shed that can’t be solved by hanging cloth bags of a drying agent such as charcoal or non-clumping kitty litter or commercial dehumidifying crystals, you may need a dehumidifier. Figure out your needed capacity and investigate the various types and models available. You may be surprised at the variations available and will find one to suit your shed.